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Author: Subject: Any comments on buying pH meters?
Artemus Gordon
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[*] posted on 4-4-2014 at 13:52
Any comments on buying pH meters?


I did try to UTFSE and found nothing about this topic, which surprises me. pH meters are available in a very wide range of prices. Anybody have good/bad experiences with certain features, models, or brands?
I assume long, thin electrodes are better than the short kind, but maybe they have reliability or accuracy issues?
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PeeWee2000
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[*] posted on 4-4-2014 at 14:29


pH meters are tricky, you need to maintain them after every use make sure you get everything you need to do this. Basically when looking for one you get what you pay for, if you buy a 10$ aquarium pH meter from china thats what you get if you get a 100$ pH meter from europe it'll work much better. http://www.ebay.com/itm/Milwaukee-MW102-Smart-pH-C-Meter-SM1... Heres the one I have it works without problem and automatically adjusts for temperature and is very easy to calibrate plus it has replacable probes. The seller sells everything you would need for it, new probes, cleaning solution, storage soluton and calibration solution. Although you can probably make the storage solution and cleaning solution fairly cheaply and easily instead of buying the overpriced ones. I wouldnt skimp out on calibration solutions though, the link I posted comes with 2 calibration packets for one time use.



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Artemus Gordon
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[*] posted on 4-4-2014 at 16:03


Thanks, PeeWee.
What about long-term storage? Is there a risk of the storage soln evaporating away, and if so, does this hurt the electrode?
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Chemosynthesis
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[*] posted on 4-4-2014 at 16:06


I'm actually really interested in any advice people have as well. I've only used high end (Corning, Milwaukee Instruments, etc.) tabletop meters for buffer formulation, and never paid too much attention to specifics as they are all easily >$300 at minimum, and not a large part of what anyone does around there. As long as you screw on the little solutions and ensure washing between contact, I have not seen any solution evaporate appreciably when capped.

Never seen this, but I don't think any damage results from allowing the glass/electrodes to dry either (though everyone taught me never to do this), though it would be really annoying to re-hydrate before use, then re-calibrate.
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Artemus Gordon
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[*] posted on 4-4-2014 at 16:12


How long would rehydration take? An hour? A day?
If it was an hour, that wouldn't bug me because I tend to do my experiments in bursts with sometimes weeks of inaction in between.
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Chemosynthesis
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[*] posted on 4-4-2014 at 16:21


Quote: Originally posted by Artemus Gordon  
How long would rehydration take? An hour? A day?
If it was an hour, that wouldn't bug me because I tend to do my experiments in bursts with sometimes weeks of inaction in between.

I'm not sure. Sorry. It would be an interesting experiment to see. I'll bet emailing a manufacturer would be fruitful.
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Artemus Gordon
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[*] posted on 4-4-2014 at 16:32


OK, I found this on eutechinst.com -

"After removing the electrode from soaking bottle or protective cap at the bottom of sensor, place the electrode in a clean container containing one of the liquids i.e. 4.0 M KCl or pH 7.0 buffer. Soak electrode for 30 minutes if left dry."

But, it also says -

"The sensor should never be stored dry. Always keep pH electrode moist. Proper pH electrode storage maximizes electrode performance and extends electrode life."

This is for glass electrodes, IDK if the same applies to junction electrodes.
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numos
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[*] posted on 4-4-2014 at 17:13


Personally I like ph paper much more, unless you need lab grade accuracy,which in that case the lab should have a good one, ph paper works fine, quick easy,and no maintenance. The meters are cumbersome and personally for home use, I'd take paper over meter any day...



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Dr.Bob
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[*] posted on 4-4-2014 at 17:38


I have to agree on pH paper, it ismuch simpler. Unless you are doing titrations and complex analytical work, 0-14 pH papers will work for most functions. But otherwise buy a mid-line ones.
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PiledhigherandDeeper
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[*] posted on 4-4-2014 at 18:10


pH meters in the teaching lab have given me fits... very finicky, with error warnings that take way too long to diagnose.

I can't speak for the accuracy, but for ease of measurements and since I am mostly interested in demonstrating the big picture concepts (pH titration curve analysis, change of temperature with time curves), I dig the Vernier hardware. Lots of options for other probes once you get an interface, pretty much plug and play, bulletproof...

http://www.vernier.com/products/interfaces/

I have a colleague that uses the Labquest interface, in intro level chem labs, as well as P-chem. CBL's are my go to.

Just my $.02.

I'll third, fourth, what has been said though... can't beat pH paper for most apps.

[Edited on 5-4-2014 by PiledhigherandDeeper]
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[*] posted on 5-4-2014 at 17:10


I bought a pH meter for 15 dollars. Guy happened to live 3 minute walk from my house! It works beautifully and I calibrated it with a can of Sprite (pH 3.8) and borax solution (pH 9.1).

So my advice is low price does not equal low quality

http://toronto.kijiji.ca/c-buy-and-sell-other-BRAND-NEW-DIGI...

[Edited on 6-4-2014 by GoldGuy]
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DrAldehyde
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[*] posted on 6-4-2014 at 10:33


I concur with meters being finicky. We use handheld meters for water test at three sites. Consistency is much more important than accuracy for us. We buy meters in the $100-$200US range. We use fresh calibration solutions, storage solutions, and cleaning solutions. What I find is I can calibrate all six meters at the same time and end up getting six readings covering a 1.0pH range. These are meters with purported accuracy to the 100ths. I don't know how they can even sell this garbage. I find if I calibrate several times, I start getting more stable readings. I end up using two meters for every test to average the results.
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